Hydrogels are cross-linked hydrophilic polymer structures that imbibe large quantities of water or biological
fluids. Hydrogels are an upcoming class of polymer-based controlled release drug delivery systems, embracing numerous
biomedical and pharmaceutical applications. Hydrogels are swellable polymeric materials, and are being widely investigated
as a carrier for drug delivery systems. Besides exhibiting swelling-controlled drug release, hydrogels also show
stimuli responsive changes in their structural network and hence leading to the drug release. The present manuscript is
concerned with the classification, method of preparation; application in drug deliveryand FDA approved market products
of hydrogels with the patent review on hydrogel composition and its manufacturing process. It also highlights recent
advances in hydrogel drug delivery especially stimuli-responsive hydrogel and its patents. This patent review is useful in
the synthesis methods of hydrogel drug delivery and its application.